Probing and Engineering the Fatty Acyl Substrate Selectivity of Starter Condensation Domains of Nonribosomal Peptide Synthetases in Lipopeptide Biosynthesis

Lipopeptides are produced by nonribosomal peptide synthetases (NRPSs) and contain diverse fatty acyl moieties that are major determinants of antibiotic potency. The lipid chains are incorporated into peptidyl backbones via lipoinitiation, a process comprising free fatty acid activation and the subsequent starter condensation domain (C1)‐catalyzed conjugation of fatty acyl moieties onto the aminoacyl substrates. Thus, a thorough understanding of lipoinitiation biocatalysts would significantly expand their potential to produce novel antibiotics. Here, biochemical assays, in silico analysis, and mutagenesis studies are used to ultimately identify the specific amino acid residues that control the fatty acyl substrate selectivity of C1 in lipopeptide A54145. In silico docking study has identified four candidate amino acids, and subsequent in vitro assays confirmed their functional contribution to the channel that controls substrate selectivity. Two engineered variants with single point mutations in C1 are found to alter the substrate selectivity toward nonnatural fatty acyl substrates. The detailed mechanistic insights into the catalytic contribution of C1 obtained from the present study will facilitate future NPRS biocatalyst efforts     

Cardiomyocyte‐specific role of miR‐24 in promoting cell survival

Cardiomyocyte cell death is a major contributing factor to various cardiovascular diseases and is therefore an important target for the design of therapeutic strategies. More recently, stem cell therapies, such as transplantation of embryonic or induced pluripotent stem (iPS) cell‐derived cardiomyocytes, have emerged as a promising alternative therapeutic avenue to treating cardiovascular diseases. Nevertheless, survival of these introduced cells is a serious issue that must be solved before clinical application. We and others have identified a small non‐coding RNA, microRNA‐24 (miR‐24), as a pro‐survival molecule that inhibits the apoptosis of cardiomyocytes. However, these earlier studies delivered mimics or inhibitors of miR‐24 via viral transduction or chemical transfection, where the observed protective role of miR‐24 in cardiomyocytes might have partially resulted from its effect on non‐cardiomyocyte cells. To elucidate the cardiomyocyte‐specific effects of miR‐24 when overexpressed, we developed a genetic model by generating a transgenic mouse line, where miR‐24 expression is driven by the cardiac‐specific Myh6 promoter. The Myh6‐miR‐24 transgenic mice did not exhibit apparent difference from their wild‐type littermates under normal physiological conditions. However, when the mice were subject to myocardial infarction (MI), the transgenic mice exhibited decreased cardiomyocyte apoptosis, improved cardiac function and reduced scar size post‐MI compared to their wild‐type littermates. Interestingly, the protective effects observed in our transgenic mice were smaller than those from earlier reported approaches as well as our parallelly performed non‐genetic approach, raising the possibility that non‐genetic approaches of introducing miR‐24 might have been mediated via other cell types than cardiomyocytes, leading to a more dramatic phenotype. In conclusion, our study for the first time directly tests the cardiomyocyte‐specific role of miR‐24 in the adult heart, and may provide insight to strategy design when considering miRNA‐based therapies for cardiovascular diseases.     

新疆额尔齐斯河流域冷水鱼肠道耐低温乳酸菌的分离筛选及其遗传差异

[目的]从新疆阿勒泰地区额尔齐斯河流域冷水鱼肠道中分离耐低温的乳酸菌,挖掘乳酸菌的物种和遗传多样性,为低温乳酸菌生物技术研发提供优良菌种.[方法]利用MRS、Elliker两种不同培养基从9种冷水鱼肠道中,分离筛选出耐低温菌,测定细菌最适生长温度并进行常规生理生化实验.根据16S rRNA基因序列初步确定耐低温菌的系统进化地位,并采用BOX、(GTG)5、ERIC三种不同的引物进行rep-PCR,对16S rRNA基因高度同源性的菌株进一步区分.[结果]分离得到78株耐冷菌,最终确定有24株为耐低温乳酸菌,菌株的最适生长温度在15-24℃之间.系统发育分析结果表明:24株耐低温乳酸菌隶属于6个属,其中肉杆菌属(Carnobacterium)3株,乳球菌属(Lactococcus)9株,肠球菌属(Enterococcus)7株,环丝菌属(Brochothrix)1株,魏斯氏菌属(Weissella)2株,链球菌属(Streptococcus)2株.指纹图谱聚类分析树状图显示乳球菌属(Lactococcus)和肠球菌属(Enterococcus)存在种及菌株水平上的遗传差异,前者包括4个种,后者2个种.[结论]新疆额尔齐斯河流域冷水鱼肠道中分离的耐低温乳酸菌以球菌为主,没分离到常见的乳杆菌,需进一步完善分离培养的方法,深入挖掘和研究其物种多样性和遗传多样性.     

MV-mimicking micelles loaded with PEG-serine-ACP nanoparticles to achieve biomimetic intra/extra fibrillar mineralization of collagen in vitro

Since their discovery, matrix vesicles (MVs) containing minerals have received considerable attention for their role in the mineralization of bone, dentin and calcified cartilage. Additionally, MVs' association with collagen fibrils, which serve as the scaffold for calcification in the organic matrix, has been repeatedly highlighted. The primary purpose of the present study was to establish a MVs–mimicking model (PEG-S-ACP/micelle) in vitro for studying the exact mechanism of MVs-mediated extra/intra fibrillar mineralization of collagen in vivo. In this study, high-concentration serine was used to stabilize the amorphous calcium phosphate (S-ACP), which was subsequently mixed with polyethylene glycol (PEG) to form PEG-S-ACP nanoparticles. The nanoparticles were loaded in the polysorbate 80 micelle through a micelle self-assembly process in an aqueous environment. This MVs–mimicking model is referred to as the PEG-S-ACP/micelle model. By adjusting the pH and surface tension of the PEG-S-ACP/micelle, two forms of minerals (crystalline mineral nodules and ACP nanoparticles) were released to achieve the extrafibrillar and intrafibrillar mineralization, respectively. This in vitro mineralization process reproduced the mineral nodules mediating in vivo extrafibrillar mineralization and provided key insights into a possible mechanism of biomineralization by which in vivo intrafibrillar mineralization could be induced by ACP nanoparticles released from MVs. Also, the PEG-S-ACP/micelle model provides a promising methodology to prepare mineralized collagen scaffolds for repairing bone defects in bone tissue engineering.     

生物经济与生物技术之浅析

生物经济是由生物技术高度产业化推动的人类历史上将达到的第四次经济浪潮,当前我们正处于生物经济的成长阶段。生物经济具有资源依赖性强,产品多样化但垄断性差,生物技术通用性强的显著特点。生物技术产业的崛起将促进新经济发展,对农业、工业、医药、环境保护、新能源开发以及生物战剂的抵御能力产生重要影响。通过总结生物经济的发展态势及现状,指出我国发展生命科学与生物技术的成果和面临的问题,探讨发展对策,以期为推动生命科学和生物技术产业化提供参考。     

水稻条叶枯病毒(RStV)基因组组分4的克隆与序列分析

利用RTPCR技术合成并扩增了水稻条叶枯病毒(RStV)中国云南分离物基因组组分4的全长cDNA,将PCR产物克隆在载体pCRII上,并进行全序列测定,所得核苷酸序列及推测的氨基酸序列与日本分离物T进行比较。结果表明,在核苷酸水平,两分离物的vORF、vcORF及基因间非编码区序列的同源性分别为94.9%、94.1%、86.1%,5’端非编码区序列相同,而3’非编码区同源性为96.1%,仅有两个核苷酸不同;在氨基酸水平,vORF及vcORF编码蛋白的同源性分别为99.4%和98.3%。可见,编码区的大小及其氨基酸序列和两末端序列都是很保守的。因此,中国云南分离物Y与日本分离物T可能有很近的亲缘关系。     

鄂西产三种野生葛总黄酮含量的紫外分光光度法测定

鄂西产三种野生葛总黄酮含量的紫外分光光度法测定李石生刘欣邓京振赵守训（中国药科大学天然药物化学教研室,南京２１００３８）Ｄｅｔｅｒｍｉｎａｔｉｏｎｏｆｔｏｔａｌｆｌａｖｏｎｏｉｄｉｎ３ｗｉｌｄｓｐｅｃｉｅｓｏｆＰｕｅｒａｒｉａｆｒｏｍＷｅｓｔＨｕｂ...     

Distributed Function Mining for Gene Expression Programming Based on Fast Reduction

For high-dimensional and massive data sets, traditional centralized gene expression programming (GEP) or improved algorithms lead to increased run-time and decreased prediction accuracy. To solve this problem, this paper proposes a new improved algorithm called distributed function mining for gene expression programming based on fast reduction (DFMGEP-FR). In DFMGEP-FR, fast attribution reduction in binary search algorithms (FAR-BSA) is proposed to quickly find the optimal attribution set, and the function consistency replacement algorithm is given to solve integration of the local function model. Thorough comparative experiments for DFMGEP-FR, centralized GEP and the parallel gene expression programming algorithm based on simulated annealing (parallel GEPSA) are included in this paper. For the waveform, mushroom, connect-4 and musk datasets, the comparative results show that the average time-consumption of DFMGEP-FR drops by 89.09%%, 88.85%, 85.79% and 93.06%, respectively, in contrast to centralized GEP and by 12.5%, 8.42%, 9.62% and 13.75%, respectively, compared with parallel GEPSA. Six well-studied UCI test data sets demonstrate the efficiency and capability of our proposed DFMGEP-FR algorithm for distributed function mining.     

荸荠营养器官的发育与解剖学研究

荸荠同化茎起源于肉质主茎倒２或倒３叶的叶腋内。同化茎基部着生二鞘状叶,鞘状叶对早期同化茎穿出土面具保护作用。匍匐茎大多起源于同化茎基部鞘状叶的叶腋内。当植株开始抽生花茎时,地下匍匐茎顶端开始膨大。球茎的膨大是匍匐茎顶端５－６节的基本组织经细胞有丝分裂,增加细胞数目,然后由细胞体积的扩大来实现的。球茎具足够的营养物质供来年顶芽萌发的需要,故属水生植物冬芽的性质。